Choshu, "long state," is the common name for the Japan
ese feudal domain
, located at the western tip of Honshu
in modern-day Yamaguchi prefecture
. During the rise of Tokugawa Ieyasu
in the 1590's and 1600's, Choshu was one of the key "tozama domains
" opposed to his rule, and its samurai were among those opposing him at Sekigahara
After quieting down for a couple of centuries, Choshu again rose to prominence following the opening of Japan in 1854, as it straddled the strait of Shimonoseki, where European and American ships would enter the Inland Sea, bound for Kobe and ports in the east.
In 1863, the Imperial court in Kyoto decided that the opening of Japan had been a bad idea, and passed along an order to the Edo bakufu to sonno joi, "revere the emperor and expel the barbarians," as many samurai in Choshu and Satsuma had been advocating. Choshu began posting artillery along the strait to pick off foreign ships as they arrived in Japan. This led to a massive four-nation bombardment of Choshu in August of 1864, after which the bakufu had to pay 2.2 million ryo in reparations to the Europeans.
In 1866, Choshu allied itself with Satsuma and began a serious campaign against the shogun, which eventually culminated in the removal of the shogun and restoration of Emperor Meiji's power (the Meiji Restoration). Many of Choshu's native sons became key players in the early Japanese government: Ito Hirobumi, Inoue Kaoru, and Yamagata Aritomo were all Choshu natives within the ranks of the genro.
Purely by coincidence, the Choshu area is now a yakuza hot spot.
* thanks to mauler for reminding me...